My Onkyo Integra DTR-7 receiver is an early production run unit. It is virtually an enhanced TX-DS777 with gold jacks added. These early run units were known for center channel hiss/hum noise. There was a very simple fix for this issue. Onkyo recalled most of the early models and fixed them. I would like to perform this fix myself but I cannot find any reference to it. I have a copy of the service manual but it does not mention an update to early production runs. Is there anyone here familiar with this repair that can advise me. Thank you.